First, Apple is doing all it can to hit its projected 12-hour battery life figure: the 2013 Air now includes a 7150mAh battery, up very slightly from the 6700mAh battery in the 2012 Air.

Be very careful when quoting battery numbers. The amp-hour rating is only one part of a battery's capacity. The voltage is up slightly with this battery too, from 7.3 to 7.6V. If you go by the mAh rating alone, you get a 6.7% increase from the previous generation's battery. When you factor the voltage in to get a Wh rating, you then get a 11.1% increase from the previous generation. The Ah rating cannot be relied upon to compare battery capacities when the voltages differ.

"the 6.0 Gbps transfer speeds of SATA III are actually getting a little slow for modern SSD controllers and flash memory"

As someone who finally upgraded his PC to SATA3 with a high speed SSD last October, this sentence makes me a little sad.

Eh, at least you're closer to getting the most out of your SATA interface. Beats the other way 'round we had for years and years when a spinning HD would only saturate ATA-33 for a split second while the cache was being emptied.

"the 6.0 Gbps transfer speeds of SATA III are actually getting a little slow for modern SSD controllers and flash memory"

As someone who finally upgraded his PC to SATA3 with a high speed SSD last October, this sentence makes me a little sad.

I wouldn't get too sad. The impact on real world performance is virtually nil. Someone did a comparison of SATA2 vs. SATA3 for SSD, and showed that while the difference was huge in synthetic tests, it was fractions of a second in real use. This further limitation beyond SATA3 will be considerably smaller.

Does anyone know what the extra 512MiB (Hynix H5TC4G63AFR 4 Gb synchronous DRAM) on the logic board is for? A reply to my question on the tear down mentioned PSR (Panel Self Refresh), but AFAIK that's handled by the TCON (Timing Controller) on the display itself.

Can Haswell's iGPU use RAM that's dedicated to it rather than share the main system RAM?

"the 6.0 Gbps transfer speeds of SATA III are actually getting a little slow for modern SSD controllers and flash memory"

As someone who finally upgraded his PC to SATA3 with a high speed SSD last October, this sentence makes me a little sad.

Considering it is (or at least was) a bit of a pain in the ass to get an OS to boot off a PCI-E drive, you can feel a bit less sad. It is quite possibly a Mac-only pleasure for now.

But then again, us PC users can upgrade and get big proper raid controllers running on PCI-E 8x or higher for some true performance.

I have a revo drive in my workstation and its pretty easy to do a fresh install. Just need a compatible mobo, boot the windows installer, insert driver cd for the pcie drive, continue install.

That said I have this feeling that ms will start including basic drivers for these pcie drives. Just enough to let the install and boot happen without needing a driver cd.

I'm not too sure if there will be a huge performance increase for air users. You need a lot of data to really notice the difference. The only place outside benchmarks that I saw a huge difference was in my simulations. After my 32gb of ram runs out, it writes all the data to the drive. So that became much faster.

My gut days this is more of a cost thing. If every notebook is using the same drive it will be cheaper for apple. Probably why they didn't brag about it.

Does anyone know what the extra 512MiB (Hynix H5TC4G63AFR 4 Gb synchronous DRAM) on the logic board is for? A reply to my question on the tear down mentioned PSR (Panel Self Refresh), but AFAIK that's handled by the TCON (Timing Controller) on the display itself.

Can Haswell's iGPU use RAM that's dedicated to it rather than share the main system RAM?

Yes. That's what Crystalwell eDRAM is for on the GT3e iGPU parts. As I understand, the MBA uses the regular GT3 parts without the eDRAM, so it's probably not for the iGPU.

First, Apple is doing all it can to hit its projected 12-hour battery life figure: the 2013 Air now includes a 7150mAh battery, up very slightly from the 6700mAh battery in the 2012 Air.

Be very careful when quoting battery numbers. The amp-hour rating is only one part of a battery's capacity. The voltage is up slightly with this battery too, from 7.3 to 7.6V. If you go by the mAh rating alone, you get a 6.7% increase from the previous generation's battery. When you factor the voltage in to get a Wh rating, you then get a 11.1% increase from the previous generation. The Ah rating cannot be relied upon to compare battery capacities when the voltages differ.

Give this person a medal!

I've been trying to get writers to clue into this for years. Bravo! A first year physics/E&M course, or at least a basic knowledge of the difference between power, energy and current should be a mandatory job requirement for technology writers. Sadly, almost all of them quote mAh as the capacity of an anonymous battery when it absolutely is not.

First, Apple is doing all it can to hit its projected 12-hour battery life figure: the 2013 Air now includes a 7150mAh battery, up very slightly from the 6700mAh battery in the 2012 Air.

Be very careful when quoting battery numbers. The amp-hour rating is only one part of a battery's capacity. The voltage is up slightly with this battery too, from 7.3 to 7.6V. If you go by the mAh rating alone, you get a 6.7% increase from the previous generation's battery. When you factor the voltage in to get a Wh rating, you then get a 11.1% increase from the previous generation. The Ah rating cannot be relied upon to compare battery capacities when the voltages differ.

You are absolutely correct. Power is measured in watts, not amps. Multiply amps by voltage to get the watt rating.

"the 6.0 Gbps transfer speeds of SATA III are actually getting a little slow for modern SSD controllers and flash memory"

As someone who finally upgraded his PC to SATA3 with a high speed SSD last October, this sentence makes me a little sad.

Considering it is (or at least was) a bit of a pain in the ass to get an OS to boot off a PCI-E drive, you can feel a bit less sad. It is quite possibly a Mac-only pleasure for now.

But then again, us PC users can upgrade and get big proper raid controllers running on PCI-E 8x or higher for some true performance.

I have a revo drive in my workstation and its pretty easy to do a fresh install. Just need a compatible mobo, boot the windows installer, insert driver cd for the pcie drive, continue install.

That said I have this feeling that ms will start including basic drivers for these pcie drives. Just enough to let the install and boot happen without needing a driver cd.

I'm not too sure if there will be a huge performance increase for air users. You need a lot of data to really notice the difference. The only place outside benchmarks that I saw a huge difference was in my simulations. After my 32gb of ram runs out, it writes all the data to the drive. So that became much faster.

My gut days this is more of a cost thing. If every notebook is using the same drive it will be cheaper for apple. Probably why they didn't brag about it.

Jim

Anything that brings storage speeds closer to RAM speeds is a good thing. This will be very useful with swapping virtual pages in and out. And for those who think that small gains don't matter, well, it's gotten to the point that any time we lift our finger from a key we expect the operation be be completed. The closer we get to that ideal the better. It's the little things that often make the experience better.

First, Apple is doing all it can to hit its projected 12-hour battery life figure: the 2013 Air now includes a 7150mAh battery, up very slightly from the 6700mAh battery in the 2012 Air.

Be very careful when quoting battery numbers. The amp-hour rating is only one part of a battery's capacity. The voltage is up slightly with this battery too, from 7.3 to 7.6V. If you go by the mAh rating alone, you get a 6.7% increase from the previous generation's battery. When you factor the voltage in to get a Wh rating, you then get a 11.1% increase from the previous generation. The Ah rating cannot be relied upon to compare battery capacities when the voltages differ.

Give this person a medal!

I've been trying to get writers to clue into this for years. Bravo! A first year physics/E&M course, or at least a basic knowledge of the difference between power, energy and current should be a mandatory job requirement for technology writers. Sadly, almost all of them quote mAh as the capacity of an anonymous battery when it absolutely is not.

Amp hours is a standard rating which works just fine with batteries that have the same voltage. But otherwise, it can just be confusing.

First, Apple is doing all it can to hit its projected 12-hour battery life figure: the 2013 Air now includes a 7150mAh battery, up very slightly from the 6700mAh battery in the 2012 Air.

Be very careful when quoting battery numbers. The amp-hour rating is only one part of a battery's capacity. The voltage is up slightly with this battery too, from 7.3 to 7.6V. If you go by the mAh rating alone, you get a 6.7% increase from the previous generation's battery. When you factor the voltage in to get a Wh rating, you then get a 11.1% increase from the previous generation. The Ah rating cannot be relied upon to compare battery capacities when the voltages differ.

Give this person a medal!

I've been trying to get writers to clue into this for years. Bravo! A first year physics/E&M course, or at least a basic knowledge of the difference between power, energy and current should be a mandatory job requirement for technology writers. Sadly, almost all of them quote mAh as the capacity of an anonymous battery when it absolutely is not.

Amp hours is a standard rating which works just fine with batteries that have the same voltage. But otherwise, it can just be confusing.

Yeah, exactly. But many (read most) journalists quote mAh as the energy capacity of the battery. This is irritating as hell because mAh hours isn't a unity of energy. Without the voltage it could literally signify any quantity of energy, although realistically, the voltages of batteries only vary by about one order of magnitude. Still, that's a massive potential error when comparing two batteries in this manner.

Wh is directly a unity of energy.

W = J/s

So

1 Wh = (J/s) * h = 3600 J

This cannot be calculated without both the voltage and the current-time. Ars writers, please take note of this. Don't call mAh energy. It isn't energy, nor is it enough to calculate it. It cannot be used to compare two batteries of different configuration and voltage.

"the 6.0 Gbps transfer speeds of SATA III are actually getting a little slow for modern SSD controllers and flash memory"

As someone who finally upgraded his PC to SATA3 with a high speed SSD last October, this sentence makes me a little sad.

Considering it is (or at least was) a bit of a pain in the ass to get an OS to boot off a PCI-E drive, you can feel a bit less sad. It is quite possibly a Mac-only pleasure for now.

But then again, us PC users can upgrade and get big proper raid controllers running on PCI-E 8x or higher for some true performance.

I have a revo drive in my workstation and its pretty easy to do a fresh install. Just need a compatible mobo, boot the windows installer, insert driver cd for the pcie drive, continue install.

That said I have this feeling that ms will start including basic drivers for these pcie drives. Just enough to let the install and boot happen without needing a driver cd.

I'm not too sure if there will be a huge performance increase for air users. You need a lot of data to really notice the difference. The only place outside benchmarks that I saw a huge difference was in my simulations. After my 32gb of ram runs out, it writes all the data to the drive. So that became much faster.

My gut days this is more of a cost thing. If every notebook is using the same drive it will be cheaper for apple. Probably why they didn't brag about it.

Jim

Anything that brings storage speeds closer to RAM speeds is a good thing. This will be very useful with swapping virtual pages in and out. And for those who think that small gains don't matter, well, it's gotten to the point that any time we lift our finger from a key we expect the operation be be completed. The closer we get to that ideal the better. It's the little things that often make the experience better.

Agreed. I never did a comparison test of my old Vertex3 SSD before I got my REVO... Its in my 2010 MBP now, but I doubt that would be fair. Anyway, here is what we have to look forward to (bench mark from my revo):

This cannot be calculated without both the voltage and the current-time. Ars writers, please take note of this. Don't call mAh energy. It isn't energy, nor is it enough to calculate it. It cannot be used to compare two batteries of different configuration and voltage.

I appreciate what everyone is trying to get at here, but I'd recommend taking it all with a large dose of salt.

A typical Li-ion cell is given a nominal rating of 3.7V, but it will provide from 4.2V down to around 3V (before damaging the cell) over a single discharge cycle. Note that the 7.3V and 7.6V numbers indicate two series cells of 3.65V and 3.8V, respectively. Do those numbers actually indicate a difference in the voltage provided by the cell over its discharge cycle? You're willing to read that nominal number and just run with it? What do you think the marketing department is thinking about right now?

If you want to get a better idea how much power you can draw from these batteries, you'd need to connect them to a typical load profile for your application and measure the instantaneous power produced through the discharge cycle. Then to do it one better, you'd want to repeat the experiment and see how the cells degrade over time. Barring that, I'm as happy to evaluate batteries with the Ah number by itself as I am to consider the nominal voltage. In fact I'd prefer just the Ah number, because that tells me important information about the maximum charge rate of the cell. I don't know what that voltage number is saying. Voltage numbers smell a little too much like monitor diagonal measurements from back in the CRT days.

This cannot be calculated without both the voltage and the current-time. Ars writers, please take note of this. Don't call mAh energy. It isn't energy, nor is it enough to calculate it. It cannot be used to compare two batteries of different configuration and voltage.

I appreciate what everyone is trying to get at here, but I'd recommend taking it all with a large dose of salt.

A typical Li-ion cell is given a nominal rating of 3.7V, but it will provide from 4.2V down to around 3V (before damaging the cell) over a single discharge cycle. Note that the 7.3V and 7.6V numbers indicate two series cells of 3.65V and 3.8V, respectively. Do those numbers actually indicate a difference in the voltage provided by the cell over its discharge cycle? You're willing to read that nominal number and just run with it? What do you think the marketing department is thinking about right now?

If you want to get a better idea how much power you can draw from these batteries, you'd need to connect them to a typical load profile for your application and measure the instantaneous power produced through the discharge cycle. Then to do it one better, you'd want to repeat the experiment and see how the cells degrade over time. Barring that, I'm as happy to evaluate batteries with the Ah number by itself as I am to consider the nominal voltage. In fact I'd prefer just the Ah number, because that tells me important information about the maximum charge rate of the cell. I don't know what that voltage number is saying. Voltage numbers smell a little too much like monitor diagonal measurements from back in the CRT days.

Yes, of course real world voltage varies, making rated voltage an imperfect representation of actual voltage across the discharge time of the cell. But you are making the same mistake the writers to: the Ah number given previous knowledge of the specific battery (are the cells in series, parallel, how many are there? What is their chemistry?) is meaningful. But it doesn't give you information about the energy without knowing the configuration of the battery. Knowing a voltage is enough to allow you to calculate this, even if the voltage across the whole cell discharge time is not known precisely. It will simply mean your calculation has some margin of error.

Ah (mAh) simply is not sufficient as an abstract representation, and should not be quoted abstractly or compared without knowledge of what the voltage is doing.

Edit: You also said: "I don't know what that voltage number is saying. Voltage numbers smell a little too much like monitor diagonal measurements from back in the CRT days."

Regardless of how accurate the rated number is, you still need it to know the capacity of the battery. If you don't trust the number printed on the battery, measure the voltage output of the battery over its life and use your own numbers. But don't quote mAh is if it means something without some estimate of the voltage pushing it. Trust the manufacturer or don't. It doesn't change the math.

Ah (mAh) simply is not sufficient as an abstract representation, and should not be quoted abstractly or compared without knowledge of what the voltage is doing.

I'm fine with this quote, but reading some nominal voltage off of a battery label does not even begin to qualify as "knowledge of what the voltage is doing."

The voltage you'll get out of any battery is a steadily decreasing value. Two batteries of the same Li-ion chemistry will not likely vary in their maximum safe charge voltage (4.2V) and they won't produce a constant voltage over time. If you're going to make a claim that battery A has a higher voltage than battery B, I want to see that expressed in a discharge chart, not a number that could have easily been picked by a dart-throwing monkey. Or are you aware of some standard for defining nominal voltage for Li-ion cells that I haven't heard of? I'd love to see a reliable standard if there is one.

Ah (mAh) simply is not sufficient as an abstract representation, and should not be quoted abstractly or compared without knowledge of what the voltage is doing.

I'm fine with this quote, but reading some nominal voltage off of a battery label does not even begin to qualify as "knowledge of what the voltage is doing."

The voltage you'll get out of any battery is a steadily decreasing value. Two batteries of the same Li-ion chemistry will not likely vary in their maximum safe charge voltage (4.2V) and they won't produce a constant voltage over time. If you're going to make a claim that battery A has a higher voltage than battery B, I want to see that expressed in a discharge chart, not a number that could have easily been picked by a dart-throwing monkey. Or are you aware of some standard for defining nominal voltage for Li-ion cells that I haven't heard of? I'd love to see a reliable standard if there is one.

It's pretty simple: "How much energy is in the battery?". That's Wh, not Ah. And it's not (Max Voltage) * (total current). It's the INTEGRAL of voltage times current... ie, the total power dissipated.

First, as mentioned by a previous poster, it's trivial to reconfigure two battery cells to provide alternately: 1Ah*2V (series), or 2Ah*1V (parallel). The total energy is equivalent in both configurations.

Second, pretty much all of that power is going through a DC/DC voltage step-down that converts small currents at high voltage to a large currents across a low voltage load. Your CPU runs on something like 1.6V, memory something like 1.2V and the current levels fed into those circuits are far higher than the current coming out of the battery. That DC/DC conversion uses a high-frequency switching circuit with negative feedback (one of the coolest things I've ever studied). If the input voltage is higher, it will consume less current. If the input voltage is lower it will consume more current. The efficiency may change slightly at different voltage levels, but for our purposes, you can consider it to be sipping energy, not current. In other words, total battery life will be far more directly related to total battery energy than to total battery current (though if you want to be pedantic, it's actually "total charge" in this context).

Ah (mAh) simply is not sufficient as an abstract representation, and should not be quoted abstractly or compared without knowledge of what the voltage is doing.

I'm fine with this quote, but reading some nominal voltage off of a battery label does not even begin to qualify as "knowledge of what the voltage is doing."

The voltage you'll get out of any battery is a steadily decreasing value. Two batteries of the same Li-ion chemistry will not likely vary in their maximum safe charge voltage (4.2V) and they won't produce a constant voltage over time. If you're going to make a claim that battery A has a higher voltage than battery B, I want to see that expressed in a discharge chart, not a number that could have easily been picked by a dart-throwing monkey. Or are you aware of some standard for defining nominal voltage for Li-ion cells that I haven't heard of? I'd love to see a reliable standard if there is one.

I share your frustration with reporting of these numbers on packages. In the real world, Li-ion batteries like those used in laptops (not cells...you don't seem to be making the distinction) are regulated (usually internally) to output a specific voltage which may or may not vary over the discharge of the individual cells within the battery depending on the quality of the regulation. The cells certainly do decrease in voltage, but this may or may not be reflected in the output of the battery.

Regardless, we care about how much energy we can get out of the battery. What we need to know is how much current it can deliver, for how long, and at what voltage, accepting that the voltage may be a changing function. Once we know these things, we can say how much energy we can get from it. If we are missing one of them, we cannot say this. In any case, for any real world reporting purpose, the number printed on the battery (but not the cells) should be perfectly adequate. If it isn't, you can simply graph the actual voltage and current over the discharge time, calculate the mean and do the calculation using the real numbers.

The only thing I think any of us are disagreeing on here is the credibility of the voltage rating on a battery. (Well there's some minor points, but I assure you I understand the difference between a battery and a cell, for example.)

I believe we all perfectly well understand simple ideas like series and parallel configurations, buck and boost voltage conversion, how to calculate power and anything else really relevant here, at least as far as basic electrical concepts go. Can we take that as a given for a moment?

Changing the volume of the battery can easily change the maximum stored charge, but does nothing to the voltage over discharge. To change that, you're messing with battery chemistry, because the electrical potential of a given type of chemical reaction is constant. So have Apple's battery suppliers implemented a new chemistry here? Or did someone just tweak a number? Or maybe someone is regulating to a different constant output voltage as andy16666 suggests, trading current for voltage?

Me, I'll stick with mAh as a first order estimate of stored energy, and wait for an actual measured energy number before I start claiming I have anything more credible.

In other words, total battery life will be far more directly related to total battery energy than to total battery current (though if you want to be pedantic, it's actually "total charge" in this context).

While this is normally true, but to my understanding, the effective capacity of a lithium ion battery also decreases when it's discharged at high rates (and conversely, lower rate increases effective capacity). So if a system uses, say, 20% less power, it's possible to get more than 20% more battery time even from the same battery.

In other words, total battery life will be far more directly related to total battery energy than to total battery current (though if you want to be pedantic, it's actually "total charge" in this context).

While this is normally true, but to my understanding, the effective capacity of a lithium ion battery also decreases when it's discharged at high rates (and conversely, lower rate increases effective capacity). So if a system uses, say, 20% less power, it's possible to get more than 20% more battery time even from the same battery.

Agreed, which is why I pointed out in my first comment that "you'd need to connect them to a typical load profile for your application and measure the instantaneous power produced through the discharge cycle."

I'm curious, are people voting my comments down because they know something I don't, or just because they don't like the idea of being skeptical of different voltage ratings on batteries that use fundamentally the same chemistry? I'm not getting why this is controversial.

I'd love to hear from someone who has a good understanding of things like anode/cathode structure and internal resistance, because maybe there's something interesting there that would impact battery ratings as well. So far it doesn't seem that any of us are competent to speak to that kind of issue.

In other words, total battery life will be far more directly related to total battery energy than to total battery current (though if you want to be pedantic, it's actually "total charge" in this context).

While this is normally true, but to my understanding, the effective capacity of a lithium ion battery also decreases when it's discharged at high rates (and conversely, lower rate increases effective capacity). So if a system uses, say, 20% less power, it's possible to get more than 20% more battery time even from the same battery.

...

I'm curious, are people voting my comments down because they know something I don't, or just because they don't like the idea of being skeptical of different voltage ratings on batteries that use fundamentally the same chemistry? I'm not getting why this is controversial.

If I were to guess, it's because you keep saying things like this:

"Me, I'll stick with mAh as a first order estimate of stored energy, and wait for an actual measured energy number before I start claiming I have anything more credible."

when people have explained to you again and again that mAh is NOT an estimate of stored energy. It is one component of stored energy which cannot, on its own, be used as an estimate of stored energy. That's because isn't one!!!

I'm also puzzled by your continued assertion that the charge figures are somehow more reliable than the voltage ones. Considering that most devices require a particular voltage to operate at all, battery manufacturers much more commonly fudge the charge numbers. Two 7.6v batteries I received last month were both rated 1500mAh, but turned out to be relabeled 1000mAh models.

If you're going to be paranoid, I have no idea why you're trusting the charge numbers. Let alone why you're fudging the math and pretending they tell you something about the stored energy. Your whole angle seems incredibly inane. You pretend to agree and then you fall back on the same faulty arguments again and again.

I'd love to hear from someone who has a good understanding of things like anode/cathode structure and internal resistance, because maybe there's something interesting there that would impact battery ratings as well. So far it doesn't seem that any of us are competent to speak to that kind of issue.

I think it's extremely unlikely that anyone is going to invest the time into explaining such things (which I would normally be more than happy to do) to someone who stubbornly refuses to grasp the basics. It seems like an incredible waste of time to me.

I'm curious, are people voting my comments down because they know something I don't, or just because they don't like the idea of being skeptical of different voltage ratings on batteries that use fundamentally the same chemistry? I'm not getting why this is controversial.

I also keep thinking I've addressed this and apparently I haven't. The voltage of a battery does not necessarily depend on the chemistry because more complex batteries (like li-ions which require complex circuitry to charge) are internally regulated to a set voltage. The voltage of the battery (but not the cells) is a design decision, not a direct result of battery chemistry. They can change it at will. Or as the case may be, a new, more efficient battery controller may be designed to operate at a different output voltage than the old one.

I know I glossed over that before, but it's already come up and been dealt with three times. It certainly makes our life a lot easier when calculating the battery capacity over trying to work with individual cells. You can essentially disregard (to an extent) what's going on inside the battery, although things like shortened life under heavy load still play a role. This is where internal resistance plays a key role, although so does the ability of the regulation circuitry to handle the higher power output.

I also keep thinking I've addressed this and apparently I haven't. The voltage of a battery does not necessarily depend on the chemistry because more complex batteries (like li-ions which require complex circuitry to charge) are internally regulated to a set voltage.

I also keep thinking I've addressed this and apparently I haven't. The voltage of a battery does not necessarily depend on the chemistry because more complex batteries (like li-ions which require complex circuitry to charge) are internally regulated to a set voltage.

I also keep thinking I've addressed this and apparently I haven't. The voltage of a battery does not necessarily depend on the chemistry because more complex batteries (like li-ions which require complex circuitry to charge) are internally regulated to a set voltage.

That's just passing the buck.

I'm not sure how that's relevant.

I'm not sure I even believe it's true, to be frank.

Yes, Li-ion batteries require careful charge monitoring circuitry. That circuitry may be internal to the battery or it may be implemented in the device; in the case of something like a MacBook Air with its built-in battery, the distinction is pretty much academic.

And yes, regulation is required to convert energy from the battery to appropriate voltage levels for the circuitry in the computer. But as DDopson points out, those voltages are going to be numbers like 1.2V, 1.6V, maybe 1.8V and 3.3V for different parts of the device; hell there's probably a boost regulator to drive the fan at 5V or 12V, if nothing else. Absolutely nothing in that computer is going to work at a regulated 3.65V or 3.8V. (Go ahead, find a datasheet off of findparts.com that specifies a supply voltage in that range. I'll wait...)

But here's the problem with your "internally regulated to set voltage" battery theory; switching voltage regulators have an efficiency that will max out somewhere between 80% to 95%, depending on design. In a device where power efficiency is everything, who in their right mind is going to push power through a series of two voltage regulators to achieve their required final voltages?

Charge control circuitry I'll grant you, although its irrelevant to this discussion. Internal regulation to 3.8V? Unlikely in the extreme.

I'm curious, are people voting my comments down because they know something I don't, or just because they don't like the idea of being skeptical of different voltage ratings on batteries that use fundamentally the same chemistry? I'm not getting why this is controversial.

If I were to guess, it's because you keep saying things like this:

"Me, I'll stick with mAh as a first order estimate of stored energy, and wait for an actual measured energy number before I start claiming I have anything more credible."

when people have explained to you again and again that mAh is NOT an estimate of stored energy. It is one component of stored energy which cannot, on its own, be used as an estimate of stored energy. That's because isn't one!!!

If I were to guess, I'd start by noting that every time you respond to someone you disagree with, the post you're responding to has a -1 on it. But that would be petty, and no one in this discussion is being petty, are they?

Quote:

I'm also puzzled by your continued assertion that the charge figures are somehow more reliable than the voltage ones. Considering that most devices require a particular voltage to operate at all, battery manufacturers much more commonly fudge the charge numbers. Two 7.6v batteries I received last month were both rated 1500mAh, but turned out to be relabeled 1000mAh models.

Well that just sounds like you're buying batteries off of Deal Extreme. I doubt the likes of Apple are going to shop there.

Quote:

If you're going to be paranoid, I have no idea why you're trusting the charge numbers. Let alone why you're fudging the math and pretending they tell you something about the stored energy. Your whole angle seems incredibly inane. You pretend to agree and then you fall back on the same faulty arguments again and again.

Does that answer your question?

Charge directly correlates to volume. Voltage (barring some sort of internal voltage regulation, which I want to see you make a case for) relates to chemistry. And perhaps structure. (Things you'd happily explain, if I'd just agree with you, apparently.)

It is completely uncontroversial that batteries have different physical volumes, and thus different charge capacities. I expect to look at a custom-designed battery and see that number be different than the number on the battery for the next device over. Changing battery voltage "at will"? Beyond ganging cells in series, I've never seen "at will" voltage changes in any cell or battery that I've ever bought or worked with. I've also never seen a battery with a built in voltage regulator on its output. Show me one, and I'll believe. If my arguments are faulty, that should be easy to demonstrate with a datasheet.

Of a particular cell, but not of a battery. If you're talking about a battery, this statement is false.

"Voltage (barring some sort of internal voltage regulation, which I want to see you make a case for) relates to chemistry. And perhaps structure. "

Voltage relates to the chemistry of cells. When you're talking about simple batteries, it relates to chemistry and configuration. When you're talking about laptop batteries, you're essentially talking about a regulated power supply which will supply a particular voltage according to its design.

"It is completely uncontroversial that batteries have different physical volumes, and thus different charge capacities."

Again, you are talking about cells, not batteries, whilst failing to make any distinction.

"Changing battery voltage "at will"? Beyond ganging cells in series, I've never seen "at will" voltage changes in any cell or battery that I've ever bought or worked with."

I was referring to the designer, who could supply a battery which would supply x volts using any given internal storage cell they choose.

"I've also never seen a battery with a built in voltage regulator on its output. "

I've worked on many laptop batteries, and this is exactly how they are built. Here's an image of a controller board from inside a laptop battery:

One cannot safely recharge a li-ion cell without complex monitoring circuitry. The cells do not self terminate their charge cycles and will explode if overcharged. If used directly (unregulated) the voltage would fluctuate too much to drive complex electronics like a laptop. The only way to do it is to have a smart battery.